Acoustic device



April 24,1928.

E. GERLACH ACOUSTIC DEVICE Filed Nov. s. 1926 nun - J. I J7 lRr erat'orErwin fflll CH /EIMQ z/f Patented A r. 24, 1928. UNITED STATES PATENTOFFICE. I

ERWIN GEELACH, E BERLIN-SIEMENSSTADT, GERMANY, ASSIGNOR T0 SIEMENS &HALSKE, AKTIENGESELLSGHAFT, or SIEMENNSSTADT, NEAR BERLIN, GERMANY,

A. CORPORATION OF GERMANY.

ACOUSTIC DEVICE.

Application filed November 5, 1926, Serial No. 146,333, and in GermanyAugust 11, 1925.

My invention relates to improvements in acoustic devices, particularlyto a special diaphragm arrangement for acoustic devices such as electricloud-speaking or microphone apparatus. It is the principal object of myinvention to secure an especially pure transmission and a goodreproduction of the sound waves or oscillations.

.Accordingto this invention the diaphragm constructed with a surfacewhich may be produced by simply folding a smooth or fiat plate ofsuitable material, the individual portions of which are bent in anoutward direction parallel to the edge of the fold.

' Preferably, an electrodynamic system is employed for producing theoscillations of the diaphragm. For this purpose, the oscillat-.

ing edge at the junction of the two portions of the plate is disposed inan electromagnetic field and carries a metallic rib which is fed withthe alternatin or fluctuating electric currents correspon ing to speech,music, or other sounds, or in other words,

telephonic currents. Of course the diaphragm may be constructed of twobent plates connected at one side. Through the electrically transmittedsound energy the common edge of the two plates is moved in such a mannerthat the oscillations pass uniformly longitudinal into the halves of thediaphragm whilst, by suitable selection of the curvature of thediaphragm surfaces,

provision is made for the oscillations being converted into transversediaphragm oscillations. The diaphragm may suitably be made of especiallylight metal or insulating material such as common or hard paper(pertina-X) and the like.

In the accompanying drawings several embodinients of my invention areillustrated diagrammatically. The drawingsrepresent the invention asfollows:

Fig. .l is a perspective view-of one form of diaphragm embodying myinvention; Fig. 2 is a face view of magnet with parts of the diaphragmand damping means interposed between the magnet poles and the ribcarried bythe diaphragm; Fig. 3 is a fragmentary View, looking inthe'direction of the arrow 3 in Fig. 2, with parts in section,

and showing another arrangement of the damping means; Fig. 4 is adiagrammatic end view, with parts 1n section, illustrating still anotherform of my invention.

Fig. 5 is a vertical cross-section through a sound box, which may beused in connection with my invention,

Fig. 6 shows a special manner of supportin -the diaphragm,

ig. 7 is a partial cross-section through a suitable means for supportingthe dia- P g Fig. 8 shows upon an enlarged scale, some of the partsrepresented in Fig. 7 and Fig. 9 is a vertical cross-section ofanapparatus effective towards both sides.

Referrin to Fig. 1, the oscillatin edge of the diaphragm m carries as arein orcing rib l, a U-shaped sheet for instance of aluminium, embracingthe stilt edge or hold a at thejunction of the two curved diaphragmportions and riveted thereon.

Such reinforcing-metallic ribs increase the stabilityof the diaphragmsand besides afford the essential advantage of enabling me to use anelectrodynamic system for driving the diaphragms. In this case themetallic rib is disposed in a magnetic field and fed with currentcorresponding. to speech or other sounds. Another advantage of thisarrangement consists in enabling the forces for exciting the diaphragmto attack, not at a single point, but; uniformily along the stiti' edgeof the diaphragm. A bendng of this edge which otherwise may sometimeshappen when actuating the diaphragm, is made impossible because of therib, andan apparatus with such a diaphragm affords an excellentreproduction of sound and a very high acoustic power without anydisturbing noises.

The device comprises an electromagnet preferably of an extension equalto that of the metallic rib, the latter being arranged-ina ap as narrowas possible between the po es of the magnet (see Figs. 2, 3 and 9).

Care must be taken, however, that the rib can not touch the magnetpoles. For this reason, according to Figs. 2 and 3, cushions or bolstersof felt, velvet or other suitable material may be interposed between therib and the magnet poles, the bolsters thus giving an additional dampingefiect and increasing the purity in the reproduction of sound waves.Referring to these figures, Z is the conducting rib, s. is the bolsterand N, S are the magnet poles. The manner of attaching the ends of thediaphragm is shown in Fig. 4 by the way of example. Resilient ribbons,strips, wires d or the like are provided for holding the condu'ctor Zlaterally, the, individual frequency of the total magnet sys tem ispreferably'below th'e limitspofaudibility;

If the air at both sides of the diaphragm has a common connecting paththrough which the differences of air pressure produced by theoscillating diaphragm will be compensated, th'e efiiciency of thediaphragm is liable to decrease.

In Fig. 5 a means -for..av0iding the air pressure compensation isillustrated in a vertical longitudinal section. This means is asound-proof box f,.one side ofwhich is closed by means of the diaphragmm, which with its ends is attached to the edges of the box.

Oscillations of the diaphragm m are produced'by mechanism operating thestiff edge a of the diaphragm. The inner surface of the box is referablylined with sound .absorbing or amping material suchas felt or the like,in order to revent the occurrence of undesired oscillations.

. Referring to Fig. 6, a will be seen that,

instead of a box closed at one sideby the diaphragm, I may employ astructure in which the free longitudinal edges of the diaphragm m aresecured to additional bars of flange 6 which prevent the pressuredifferences from compensating each other. The construction of the meansI) may be such as to hinder air compensation from the highest just tothe lowest audible frequencies. For frequencies below this limit thecompensation causes no disturbances.

It will be understood that a rib Z such as shown in Figs. 1, 4. and 9may be also provided in Figs. 5, 6 and 7.

In the embodiments of the invention, the

outer, stationary edges of the diaphragm are fixed either to the box(Fig. 5) or to marginal pieces or bars 6. Fig. 6). In order to avoiddisturbing vibrations at the 'materials own rate, the dia hragm ispreterably secured with the ai of intermediate bolsters of felt, velvet'or'the like, as shown in Fi Z. Referring to this figure, p are A the b0sters, f is the box or a marginal piece forfsecuring the ends of thediaphragm m,

Projectin teeth at-those edges of the bolsters w 1ch touch the-diaphragmprevent the diaphragmfrom having a distinct line of clam ing.which might favour the tendency o the structure to oscillateaccording toits own rate. This constructional form is represented in Fig. 8.Referring to Fig. 9 it will be seen that two diaphragms m effectivetowards two opposite sides are provided in an apparatus of the.typedescribed; This figure 1s a crosssection through the apparatus. Thefolded diaphragms m are attached to the soundproof box f. Between thebox 7 and the ends of the di'aphragms m bolsters p are disposed in themanner described with reference to Fig. 7, the ends of the bolsters pbeing preferably .formed as shown in Fig.

8. The oscillations of the diaphragm, shown at the left of Fig. 9are-produced by electrodynamically effective means, while the diaphragmshown at the right-is electromagnetically operated. The first-nameddiaphragm m has the U-shaped metallic rib l of the type shown in Figs. 1and 4. The

rib is,arranged in the field of the electromagnet N, .5 (see Figs. 4 and9). and is sup; plied with the alternating currents for soundreproduction. Between the conducting ,rib

Z and the poles of the magnet N, S, damping bolsters s, s are clamped(see Figs. 2, 3 and .9). The stifl' edge of the other diaphragm m- (Fig.9) is attached to the armature A of an electromagnet M, the winding ofwhich is energized by the electric currents which correspond tothe soundto be reproduced.

The inner surface of the sound box 7 is lined with a sound damping orabsorbing material 2, for instance felt.

It will be understood that in Fig. 9 the two diaphragms can also bedisposed to be actuated by two similar driving systems or by means of asingle driving system. Besides, any numberof folded diaphragms of thetype described may be used in a single apparatus without departing fromthe spirit of the present invention. or instance, a plurality ofdiaphragms may be telescoped into each other with thestifi' edges or'folds adjacent to each other. It is also possible to connect the free.ends of several diaphragms for obtaininga cylindrical acoustic surface.m5

In order to protect the rather delicate diaphragm against mechanicalinjury, it is advisable to arrange a screen or network 3/, Fig. 9, orthe like of gauze or other'suitable material in front of the outer sideof the Hi! diaphragm, either directly in contact therewith. or spacedtherefrom.

vIt will be obvious to anyone skilled in the art that the devicesdescribed and shown herein may'serve for the conversion of elec- I15'trical energyinto sound energy as well as for converting. sound energyinto electrical energy withoutchanging 'th e constructional form of thedevice. In other words, any one of the devices shown may serve either121) as a telephone receiver or as a transmitter, though in thespecification in general the apparatus is assumed to be a loud spea'kerlIf the device is'used as a transmitter the oscillations of the stifi'edge will act upon an 12 electric circuit electromagnetically,-electrodynamically or by regulating a resistance.

What I claim as my invention and desire to secure by Letters Patent isl. In an acoustic device for converting electrical ener into soundenergy or sound energy into e ectrical energy, the combination of adiaphragm including two curved surfaces with a common folded edge, the.individual parts of said diaphragm'bei'ng bent outwardly in a fanlikemanner, a reinforcing metallic rib fixed to the folded edge of the saiddiaphragm, and an electro magnet system, the said rib being adapted tocarry telephonic currents and disposed be tween the poles of the saidelectromagnet system in such manner as to oscillate transversely to thelength of the rib and symmetrically to the said surfaces of thediaphragm.

2. In an acoustic device for converting: electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm including two curved surfaces with a common edge, theindividual parts of said diaphragm being bent outwardly in a fanlikemanner, a U-shaped rib, ,connected'to and embracing the said common edgeof the diaphragm, and an electromagnet system, the said U'sha ped ribbein'g adapted to carry telephonic currents and disposed between thepoles of the said electromagnet system in such manner as to oscillatetransversely to the length of the rib and symmetricallyto the individualsurfaces of the said diaphragm.

3. In an acoustic device for convertiiig electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm consisting of two curved plate members with a common edge,these plate members being bent outwardly in a fanlike manner, a U-shapededge rib of light metal riveted on and embracing the common edge of thediaphragm, and an electromagnet system, .the said edge rib being adaptedto carry telephonic currents and disposed between the poles of the saidelectromagnet system in such manner as to oscillate transversely to thelength ofthe rib and symmetrically to the individual plate members ofthe said diaphragm.

lln an acoustic device for converting electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm including two curved surfaces with a common edge, theindividual parts of said diaphragm being bent outwardly in a fanlikemanner, a reinforcing metallic rib fixed to said common edge, a magnetsystem, the said rib being'adapted to carry telephonic currents anddisposed between the poles of the said magnet system 7 in such manner asto oscillate transversely fill to the length of the rib andsymmetrically to the individual surfaces of the said diaphragm, andresilient means interposed betweenthe said rib and the poles of the saidmagnet system. r

5. In an acoustic device for converting electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm including two curved surfaces with a folded edge in common,

the individual parts of said diaphragm being the free ends of the saiddiaphragm, said walls having such an extension that the air on bothsides of the said diaphragm is prevented from compensating air pressuredifferences at least within the range of the v audible frequencies; 6.In an acoustic device for converting electrical energy into sound energyor sound energy into electrical energy, the,combination of a diaphragmincluding two curved surfaces with a folded edge in common, the

individual parts of said diaphragm being bent outwardly in afanlikemanner, a reinforcing metallic 'rib fixed to the folded edge of the saiddiaphragm, an electromagnet system, the said rib being adapted to carrytelephonic currents and disposed be tween the poles of the saidelectromagnet system in such manner as to oscillate transversely to thelength of said rib and sym- -metrically to the individual surfaces ofthe said diaphragm, and a sound proof box, to the edges of which thefree ends of the said diaphragm are attached to close said box on oneside.

In an acoustic device for converting electrical energy into sound energyor sound energy into electrical energy, the combination of a diaphragmincluding two curved surfaces with a folded edge in common, theindividual parts of said diaphragm being bent outwardly in a fan-likemanner, a reinforcing metallic rib fixed to the folded edge of the saiddiaphragm, an electromagnet sysem, the said rib being adapted to carrytelephonic currents and disposed between the poles of the saidelectromagnet system in such manner as to oscillate transversely to thelength of said rib and symctrically to the individual surfaces of thesaid diaphragm, a sound proof box, to one side of which the free ends ofthe said diaphragm are attached to close said boX on that side, andbolsters interposed between the free ends of the said diaphragm and thewall of the said box.

8. in an acoustic device for converting electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm including two curved surfaces with 'a folded edge in common,the

llll

mon, said members being bent outwardly ,in

individual parts of said diaphragm being bent outwardly in a fanlikemanner, a rein forcing metallic rib fixed to the folded edge of the saiddiaphragm, an electromagnet system, the said'rib being adapted to carrytelephonic currents and disposed between the poles of the saidelectromagnet system in such manner as to oscillate transversely to thelength of said rib and symmetrically to the'individual surfaces of thesaiddiaphragm, a soundproof box, to one side of which the free ends ofthe said diaphragm said box. I

are, attached to close said box on that side,

and a-sound damping lining on theinner tem, the said rib being adaptedtocarry telephonic currents and disposed between the poles of the saidelectromagnet system in such manner as to oscillate transversely tothe-length of said rib and symmetrically to the individual surfaces ofthe said dia-- phragm, a soundproof box to one side of which the freeends of the said diaph'ragm are attached to close said box on that side,bolsters interposed between thefree ends of the said diaphragm and theedges of the said box, and sound damping meansdisposed on the innersurface of the 10. In an acoustic device for converting electricalenergyinto sound energyor sound energy into electrical energy, thecombina tion of a diaphragm consisting of two curved plate members witha folded edge in the-said U-shaped rib being adapted to carrycommon,said membersbeing bent outwardly in a fanlike manner, a sound proof boxto one; side of which the free ends of the said members are attached toclose said box on that side, bolsters interposed between the free endsof thesaid diaphragm and the a fanlike manner, a sound proof box'to oneside of which the free ends of the said members are attached to closesaid box on that side, bolsters interposed between the free ends of thesaid diaphragm and the walls of the said'box, a U-shaped rib connectedto and embracing the folded edge of the said diaphragm, an electromagnetsystem, the'said U-shaped rib being adapted to carry telephonic currentsand /disposed between the partsof the said diaphragm being bent out-rwardly in a fanlike manner, a sound proof box to one side of which thefree ends of thesaid diaphragm are attached to close said box on thatside, bolsters interposed between the free ends of the said diaphragmand the edges of the said box, the bolsters having toothed edges incontact with the'edges of the diaphragm, a reinforcing metallic ribfixed to the connnonedge of the said diaphragm, and a magnet system, thesaid rib being disposed between the poles of the said magnet system insuch manner as to, oscillate transversely to' the length of said rib andsymmetrically to the individual surfaces of the'said diaphragm.

13. In an acoustic device 'for converting electrical energy into soundenergy or sound energy'into electricalv energy, the combination of adiaphragm consisting of two curved surfaces with a common edge, theindividual plate members connected at one edge, and V bent outwardly ina fanlike manner, a reinforcing metallic rib fixed to the common edge ofthe I said diaphragm, an electromagnet system, the said rib beingadapted to carry telephonic currents and disposed between the poles ofthe said electromagnet system in such manner as to oscillate trans:

walls of the said box,a U -shaped rib connect-. versely to the length ofsaid rib and symed to and embracing the common edge of the said members,and an electromagnet system,

telephonic currents and disposed between the poles of the saidelectromagnet system in such manner asto oscillate transversely to thelength of the rib and symmetrically to plate members with a folde edgein coman acoustic device for converting electrical energy into soundenergy or sound energy into electrical energy, the combination of adiaphragm consistin of two curved metrically to the individual membersof the said diaphragm, and a protecting network arranged on the outsideof the said diaphragm.

14. In a device ofthe character described, a diaphragm consisting of-twocurved portions, a U-shaped rib into which extend the 7 adjacent edgesof said diaphragm portions,

tions, a U-shaped rib into which extend the adjacent edges of said'diaphragm=portions,'

' said rib being free to vibrate in a direction said rib being free tovibrate in a direction transverse to itslength, and a magnet inv thefield of which said rib is located. 4

16. In a device-of the character described, I

a diaphragm consisting of adjoining curved portions, a grooved vibratoryrib embracing the adjacent edges of said diaphragm-portions, and meansfor securing the other edges of said diaphragm portions.

"edge portions are located, andan electric circuit in which said edgeportions; are 'in-Y eluded.

18. In a device of the character described, a diaphragm consisting oftwo curved sections, a vibratory conducting rib secured to saidsectionsand forming contiguous edge portions therefor, a magnet in thefield of which said rib is located, and an electric circuit in whichsaid rib is included. v

In testimony whereof I afiix my signature.

ERWIN GERLAGH.

